For a variety of reasons, it is often greatly desirable to suspend particles in liquid detergent compositions. For example, because there are certain components (e.g. bleaches, enzymes, perfumes) which readily degrade in the hostile environment of surfactant-containing detergent liquids, these components are often protected in capsule-type particles (see, for example, U.S. Pat. No. 5,281,355) and these capsule-type particles may be suspended in liquid detergent compositions. Other components which may be protected and suspended in this way are, for instance, polyvinylpyrrolidone, aminosilicones, soil release agents and antiredeposition agents. Such particles may vary significantly in size but, usually, their size is in the range of from 300 to 5000 micrometers.
Furthermore, when the liquid detergent composition is translucent or transparent, it may be desirable to suspend coloured particles or capsules of similar size in said liquid composition so as to improve the visual appearance thereof.
Shear thinning gel-type detergent compositions are generally suitable for stable suspending particles therein, since they usually have adequate viscosity when in rest or under very low shear. On the other hand, owing to their shear thinning properties, such gel-type compositions have much lower viscosity when under pouring shear.
One way of formulating such gel-type detergents is by changing a non-gelled formulation so as to form an internal structure therein which structure gives the desired properties to the thus-formed gel-type detergent.
WO-A-99/27065, WO-A-99/06519 and U.S. Pat. No. 5,820,695 disclose gel-type laundry detergent compositions having an internal structure. These documents teach systems wherein soap or fatty acid in combination with sodium sulphate and a rather specific surfactant system are used to form a gelled structure by the formation of lamellar phases.
Alternatively, shear thinning gel-type detergent compositions may be formulated by adding specific ingredients to a non-gelled detergent formulation, typically at low dosage, so as to induce gellation.
Examples of this route for preparing gelled detergents are disclosed in U.S. Pat. No. 6,362,156. More specifically, this document discloses shear thinning, transparent gel-type laundry compositions comprising a polymer gum, such as Xanthan gum, which gum is capable of forming stable continuous gum networks which can suspend particles.
However, when using a polymer additive such as the polymer gum disclosed in U.S. Pat. No. 6,362,156, so as to form the gelling structure, it is generally required to carry out several specific steps in the manufacturing process in order that the gel structure is properly formed. These steps are relatively costly and make the manufacturing process rather time-consuming.
Furthermore, while it is possible to suspend particles or capsules in a formulation disclosed by U.S. Pat. No. 6,362,156, this was found to be not straightforward: the need to suspend particles therein may give rise to significant additional restrictions on formulation flexibility. Gels structured by polymer often exhibit syneresis leading to a net movement of suspended matter, which phenomenon can only be avoided by careful choice of ingredients.
Alternatively, U.S. Pat. No. 5,952,286 discloses skin cleansing compositions comprising lamellar phase dispersions from rad micellar surfactant systems, and additionally a structurant for establishing the lamellar phase, whereby said structurant may be a fatty alcohol.
In view of the foregoing, it is an object of the present invention to find a shear thinning gel detergent formulation which does not show the above-described drawbacks.
It is another object of the invention to provide a shear thinning gel detergent formulation that is transparent and can stably suspend particles or capsules either for improving visual appearance or for practical reasons.
It is a further object to provide a shear thinning gel detergent formulation that has favourable cleaning efficacy. It has been surprisingly found that these objects could be achieved with the shear thinning gel laundry detergent composition of the present invention, containing relatively small amounts of fatty alcohol, as specified in claim 1.
Without wishing to be bound by theory, it is believed that the fatty alcohol interacts with aggregates present in the composition of the invention so as to promote the formation of planar lamellar structures similar to those found in internally structured detergent gels as e.g. disclosed by WO-A-99/27065.